Method of manufacture of one-piece composite parts with a polymer form that transitions between its glassy and elastomeric states

ABSTRACT

A polymer is formed into the shape of a one-piece composite part and then solidified by curing, setting, hardening or otherwise solidifying the polymer to form a shaped polymer form having a shape that does not draw. Composite material is laid up on the form and solidified to from the composite part. The rigidity required of the form to lay up the composite part can be provided by operating in the polymer form&#39;s glassy state, forming the shaped polymer form with a hollow core and placing a rigid insert designed to draw inside the hollow core with the polymer form in its elastomeric state or through a combination of both. In its elastomeric state the form becomes pliable (without relaxing to a different memorized shape) and can be drawn out of the one-piece composite part. Because the shape of the form does not draw, the form deforms as it is drawn. If used, the rigid insert is drawn out prior to removing the shaped polymer form. Upon removal, the polymer form in its elastomeric state returns to its original shape. The form may be used once and thrown away or reused to form multiple composite parts of the same shape.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the manufacture of one-piece composite partsincluding wings and wing shells.

2. Description of the Related Art

Known processes for fabricating castable composite parts are verycomplicated and expensive. A large portion of the complexity and expenseis associated with manufacturing related molds. Nearly any part can beconstructed as a composite part by various production methods such asfilament winding, tape placement, overbraid, chop fiber roving, coating,painting, dripping, hand lay up, resin soaked, or other compositeprocessing technique and curing process.

When these parts are manufactured using a form or mandrel, there istypically a problem with removing the form (mandrel) from the finishedpart. For very simple parts, the form can be “designed to draw” e.g. theform can be removed from the one-piece composite part by simply drawing(pulling) the form out of the part. For more complex parts such as acomposite valve 6 as shown in FIG. 1, the form 8 does not draw. Onesolution is to sacrifice or destroy the form upon removal from thefinished part. Another solution is to disassemble the form and removethe segments from the part. Another solution is to create a form thatremains part of the final composite part. Yet another solution is to usean inflatable form that can be removed by deflating the form after thecomposite part is created.

U.S. Pat. No. 7,422,714 entitled “Method Of Using A Shape MemoryMaterial As A Mandrel For Composite Part Manufacturing” is a version ofan inflatable mandrel and includes the steps of “providing a pre-formedtube of Shape Memory Polymer (SMP), using a mold to deform the SMP tubeto replicate the mold forming a SMP mandrel, filament winding resinsoaked fibers around the deformed SMP mandrel, curing the resin, causingthe deformed SMP Mandrel to return to its original smaller shape, andquickly and easily removing the SMP tube from the composite part.” (seecol. 4, lines 43-50). More particularly uncured SMP is molded to formthe tube and cured. The “tube” being the memorized shape of the SMP. Thetube is placed into a mold of the composite part, heated above its glasstransition temperature at which point the SMP transforms from a rigidsubstance to an elastic, flexible and soft substance, “inflated” intoreplicate the interior of the mold and allowed to cool to below itsglass transition temperature at which point the SMP transforms back to arigid substance. The rigid deformed SMP is removed from the mold and isready for filament winding (col. 6, lines 37-50). Once the compositepart is laid up and cured on the exterior of the deformed SMP, the SMPis heated to above its glass transition temperature inducing thedeformed SMP mandrel to relax to its memorized shape (not the inflatedmandrel shape). The tube is then removed from the composite part. (col.7, lines 21-39) The “tube” can be reused to form the same or differentcomposite parts. However, the tube must be reinflated to the desiredmandrel shape each time. This process requires a SMP that can deformfrom the memorized blank shape (tube) to the desired mandrel shape.

Air vehicles ranging from unmanned air vehicles (UAVs) of a few poundsto cruise missiles up to 10,000 pounds require strong yet lightweightand inexpensive wings. These types of air vehicles may place high loadson the wings and require the capability to maneuver rapidly. To reducethe overall cost of the air vehicles a manufacturing process forlow-cost one-piece composite wings is needed.

As shown in FIG. 2, a wing 10 can be described by its length 12(“semi-span”) measured from the “root” 14 to the tip 16, width 18(“chord length”) measured at the root from the leading edge 20 to thetrailing edge 22 and cross-section 24 as well as its taper 26, twist 28and camber 30. “Taper” indicates the rate of change of the chord length18 along the half-span of the wing from the root where the wing attachesto the airframe to the tip of the wing. Wings are tapered to control thedistribution of lift along the wing span. “Twist” indicates the rotationof the cross-section 24 along an axis 32 through the half-span of thewing. Twist is provided to avoid stalling the aircraft along the entirespan of the wing, allowing the pilot or control system time to recover.“Camber” is the asymmetry between the top and the bottom curves 34, 36of the wing in cross-section. Camber affects the lift and pitchingmoment of the wing. Camber may vary from wing root to wing tip.

A limited class of air vehicles such as model RC (radio controlled)hobby planes and other low cost air vehicles may use wings that have notaper, twist or camber. There are a few options for manufacturing thesesimple wings. One common approach is an extrusion process in whichaluminum is forced through a die having the desired wing cross-sectionto extrude the wing. Foam may be extruded in a similar process andcomposite material layed up on the foam to form the wing. In analternate process, the foam may be cut and the composite laid up. Inthis foam process, the foam remains inside the composite shell as partof the wing. In another approach, composite material is laid up on areusable form (machined or molded from a rigid material such as aluminumor steel), which is then drawn from the wing shell. The form is“designed to draw” from the composite wing shell.

A more general class of air vehicles including UAVs, munitions,missiles, and other tube or pylon launched air vehicles demand greaterperformance and may use wings formed with taper, twist and/or camber.The industry standard for manufacturing such wings is to machine thewing from a solid block of aluminum. Similarly, a block of foam can bemachined and composite material laid up to form a composite wing. Inboth processes, an expensive machining procedure is required to formeach wing that wastes considerable materials. A wing with either twistor taper cannot be extruded. A wing with twist or taper and cambercannot be laid up on a reusable form because the form will not draw outand so cannot be removed. One could form pieces of the wing e.g. top andbottom on separate rigid forms and then assemble the pieces. However,this approach does not provide a one-piece wing shell, hence wing,requires additional assembly and potentially reduces the structuralintegrity of the wing.

SUMMARY OF THE INVENTION

The following is a summary of the invention in order to provide a basicunderstanding of some aspects of die invention. This summary is notintended to identify key or critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description and the defining claims that are presentedlater.

The present invention provides a low-cost method of manufacture ofone-piece composite parts having shapes that do not draw and, inparticular, wings and wing shells with twist or taper and camber.

This is accomplished with a shaped polymer form. A polymer is fabricatedinto the shape of a form for a one-piece composite part and thensolidified by curing, setting, hardening or otherwise solidifying thepolymer. The shaped polymer form has a shape that does not draw from theone-piece composite part. Composite material is laid up on the form andsolidified to form the composite part. The stiffness desired to lay upthe composite material can be provided by operating in the polymerform's glassy state, forming the shaped polymer form with a hollow coreand placing a rigid insert designed to draw inside the hollow core orthrough a combination of both. In its elastomeric state the form becomespliable (without relaxing to a different memorized shape) and can bedrawn out of the one-piece composite part. Because the shape of the formdoes not draw, the form deforms as it is drawn. If used, the rigidinsert is drawn out prior to removing the shaped polymer form. Uponremoval, the polymer in its elastomeric state returns to its originalshape for the composite part. The form may be used once and thrown awayor reused to form multiple composite parts of the same shape. Thepolymer may be formed into the form using inexpensive processes such ascompression or injection molding. This approach does not require a SMPin that it does not utilize a memorized shape and does not require thepolymer to be inflated and reinflated into the desired form shape ateach use.

In an embodiment, a polymer is molded into the shape of a form for aone-piece composite part and solidified. The form has a shape that doesnot draw from the composite part. With the polymer in its glassy state,a composite material is laid up on the form. The composite material isthen solidified to form a one-piece composite part. The form is heatedto transition the polymer from its glassy state to its elastomeric stateand then drawn from the one-piece composite part. The act of drawingcauses the form to deform so that it can be removed. Once removed theform returns to the shape of the composite part. Polymers such as SMPsthat are mechanically sound in both their elastomeric and glassy statesare preferred.

In another embodiment, a polymer is molded into the shape of a form fora one-piece composite part and then solidified. The form has a hollowcore and a shape that does not draw from the composite part. The form isprovided with a rigid insert designed to draw from its hollow core toprovide rigidity. A composite material is laid up on the form. Thecomposite material is then solidified to form a one-piece compositepart. The rigid insert is drawn from the form and then the form in itselastomeric state is drawn from the one-piece composite part. The act ofdrawing causes the form to deform so that it can be removed. Onceremoved the form returns to its original shape. The insert may beinserted back into the polymer form and the form reused.

In another embodiment, a polymer is molded into the shape of a form fora one-piece composite part and then solidified. The form has a hollowcore and a shape that does not draw from the composite part. The form isprovided with a rigid insert designed to draw from its hollow core toprovide rigidity. The form is cooled and with the polymer in its glassystate, a composite material is laid up on the form. The compositematerial is then solidified to form a one-piece composite part. The formis heated to transition the polymer from its glassy state to itselastomeric state. The rigid insert is drawn from the form and then theform is drawn from the one-piece composite part. The act of drawingcauses the form to deform so that it can be removed. Once removed theform returns to its original shape. The insert may be inserted back intothe polymer form and the form reused.

In any of these embodiments the one-piece composite part may be aone-piece composite wing shell. A form shaped for a one-piece compositewing shell having either twist or taper and camber, and typically twist,taper and camber does not draw (without deformation). To form acomposite wing, foam is injected into each shell and solidified to forma one-piece composite wing. The foam may comprise open or closed cellfoam or syntactic foam. A wing box may be placed inside the shell foradditional structural support.

These and other features and advantages of the invention will beapparent to those skilled in the art from the following detaileddescription of preferred embodiments, taken together with theaccompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, as described above, illustrates a composite valve part for whichthe form does not draw;

FIGS. 2 a and 2 b, as described above, illustrate the twist, taper andcamber of a wing;

FIG. 3 is a flow diagram of an embodiment for manufacturing one-piececomposite wing shells by transitioning the shaped polymer form betweenits glassy and elastomeric states in accordance with the presentinvention;

FIG. 4 is a flow diagram of an embodiment for manufacturing one-piececomposite wing shells using the two-piece polymer form;

FIGS. 5 a and 5 b are diagrams of a composite wing shell filled withfoam to form the composite wing with and without a wing box,respectively; and

FIG. 6 is a flow diagram of an embodiment for manufacturing theone-piece composite valve shown in FIG. 1 using a two-piece polymerform.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a low-cost method of manufacture ofone-piece composite parts having shapes that do not draw and, inparticular, wings and wing shells with twist or taper and camber. Apolymer form is created for a one-piece composite part. This form may bemanufactured using very inexpensive manufacturing processes such ascompression or injection molding. The form does not have to be shapedduring the manufacture of the composite parts or re-shaped to reuse theform. This may dramatically reduce the capital investment required tomanufacture composite parts.

The process of manufacture using the polymer form described herein maybe applied to any one-piece composite part in which the shape of theform does not draw from the one-piece composite part formed thereon. Theterms “designed to draw” and “does not draw” are well known in theindustry. “Designed to draw” means that the form may be pulled (ordrawn) from the composite part without breaking or deforming either thecomposite part or the form. Conversely, a form that “does not draw” cannot be pulled out of the composite part, it gets stuck. For compositewing shells, any “twist” along the span of the wing will prevent theform from being drawn. Alternately, the combination of taper and camberwill prevent the form from being drawn. In many if not most airframes,the wing will exhibit twist or taper and camber and typically all three.Without loss of generality, the invention will be described for themanufacture of a composite wing shell and wing that exhibits twist,taper and camber as an exemplary embodiment of a composite part thatdoes not draw.

A polymer is fabricated into the shape of a form for a one-piececomposite part and then solidified. The shaped polymer form has a shapethat does not draw from the one-piece composite part. Composite materialis laid up on the form and then solidified to form the composite part.The stiffness desired to lay up the composite material can be providedby operating in the polymer form's glassy state, forming the shapedpolymer form with a hollow core and placing a rigid insert designed todraw inside the hollow core or through a combination of both. In itselastomeric state the form becomes pliable (without relaxing to adifferent memorized shape) and can be drawn out of the one-piececomposite part. Because the shape of the form does not draw, the formdeforms as it is drawn. If used, the rigid insert is drawn out prior toremoving the shaped polymer form. Upon removal, the polymer in itselastomeric state returns to its original shape for the composite part.The form may be used once and thrown away or reused to form multiplecomposite pans of the same shape.

A polymer is a large molecule (macromolecule) composed of repeatingstructural units typically connected by covalent chemical bonds. Whilepolymer in popular usage suggests plastic, the term actually refers to alarge class of natural and synthetic materials with a variety ofproperties and purposes. Many polymers are malleable which allows themto be cast, pressed, or extruded into an enormous variety of shapes.Polymers can be classified as thermoplastic and thermoset, elastomer,structural, biodegradable, electrically conductive, etc. Polymers areprovided in a “stored state” in which the polymer may be a liquid orsolid or at various stages of cure. Once shaped, the polymers are then“solidified” by curing, setting, hardening or otherwise solidifying.Many polymers such as elastomers cross-link when solidified. Otherpolymers such as thermoplastics do not cross-link. Polymers and theircharacteristics and methods of formulating polymers to achieve thedesired characteristics are well known in the art.

Once solidified, a parameter of particular interest in synthetic polymermanufacturing is the glass transition temperature (T_(g)), whichdescribes the temperature at which amorphous polymers undergo asecond-order phase transition from a rubbery, viscous amorphous solid(“elastomeric state”) to a brittle, glassy amorphous solid (“glassystate”). The glass transition temperature may be engineered by alteringthe degree of branching or crosslinking in the polymer or by theaddition of plasticizer. Certain polymer's such as elastomers aredesigned to optimize their mechanical properties in the elastomericstate. Other polymers such as a polymer matrix composite are designed tooptimize their mechanical properties in the glassy state. Young'sModulus quantifies the elasticity of the polymer. It is defined, forsmall strains, as the ratio of rate of change of stress to strain. Liketensile strength, this is highly relevant in polymer applicationsinvolving the physical properties of polymers. The modulus is stronglydependent on temperature. A polymer's Young's Modulus in its glassystate is typically at least 2-3 orders of magnitude greater than in itselastomeric state e.g. the polymer is much stiffer or rigid.

Shape Memory Polymers (SMPs) derive their name from their inherentability to return to their original “memorized” shape after undergoing ashape deformation. SMPs that have been preformed can be deform to anydesired shape while in their elastomeric state, cooled to transition totheir glassy state to “lock” in the desired shape and used for somepurpose such as a mandrel in Cornerstone's manufacturing process. Oncethe deformation is locked in, the polymer network cannot return to arelaxed state due to thermal barriers. The SMP will hold its deformedshape indefinitely. Thereafter, the SMP is heated to above its Tgwhereat the SMP stored mechanical strain is released and the SMP returnsto its preformed state. SMPs are used in applications in which theability to use the polymer in a desired deformed shape and then returnto the “memorized” shape is required. To support the transition betweenthe desired shape and the relaxed memorized shape the SMP must bemechanically stable in both its glassy and elastomeric states.

Several known polymer types exhibit shape memory properties. Probablythe best known and best researched polymer type exhibiting shape memorypolymer properties is polyurethane polymers. Gordon, Proc of First Intl.Conf. Shape Memory and Superelastic Tech., 115-120 (1994) and Tobushi etal., Proc of First Intl. Conf. Shape Memory and Superelastic Tech.,109-114 (1994) exemplify studies directed to properties and applicationof shape memory polyurethanes. Another polymeric system based oncrosslinking polyethylene homopolymer was reported by S. Ota, Radiat.Phys. Chem. 18, 81 (1981). A styrene-butadiene thermoplastic copolymersystem was also described by Japan Kokai, JP 63-179955 to exhibit shapememory properties. Polyisoprene was also claimed to exhibit shape memoryproperties in Japan Kokai JP 62-192440. Another known polymeric system,disclosed by Kagami et al., Macromol. Rapid Communication, 17, 539-543(1996), is the class of copolymers of stearyl acrylate and acrylic acidor methyl acrylate. Other SMP polymers known in the art includesarticles formed of norbornene or dimethaneoctahydronapthalenehomopolymers or copolymers, set forth in U.S. Pat. No. 4,831,094.Additionally, styrene copolymer based SMPs are disclosed in U.S. Pat.No. 6,759,481 which is incorporated herein by reference.

A process of manufacture of one-piece composite wing shells 50 havingtaper, twist and camber using a polymer form 52 that transitions betweenits glassy and elastomeric states is illustrated in FIG. 3.

In step 1, a polymer (in its stored state) is produced into the shape ofa polymer form 52 for the one-piece composite wing shell 50 and thencured, set, hardened or otherwise solidified (“solidified”). The formreflects the specified twist or taper and camber, likely all three, ofthe wing shell design. As such the form “does not draw” from thecomposite part as commonly understood in the industry. In sizing theform, the desired thickness of the finished composite part is taken intoaccount such that the desired final dimensions will be achieved. Theform may be solid or have a hollow core.

A polymer such as an SMP is selected that has acceptable mechanicalproperties in both its glassy and elastomeric states. Virtually anypolymer family can be made in an SMP formulation today. The choice as towhich polymer is used to produce the form will be driven first by anycompatibility requirements of the intended composite materials, andsecond by convenience (primarily cost and availability).

The form may be produced using a standard manufacturing process such ascompression or injection molding. An alternate method of producing theform could consist of first growing an SLS (selective laser sintering)pattern out of a common UV curable plastic (such as a nylon, there aremultiple off the shelf formulations available) in the shape anddimensions of the desired form, then casting a plastic such as epoxyaround the SLS pattern to create a mold, removing the SLS pattern fromthe mold, and finally, casting the elastomeric or SMP form inside themold. An aspect of this process is the ability to use inexpensivemanufacturing processes to produce the form in its final shape forlaying up the composite part. The form does not have to be shaped duringthe manufacture of the composite parts themselves or re-shaped to reusethe form. This may dramatically reduce the capital investment requiredto manufacture composite parts.

In step 2, composite materials 54 are laid up on polymer form 52. Toprovide the required stiffness or rigidity to lay up the materials, thepolymer form is in its glassy state. After curing or drawing from apreviously manufactured composite shell, the polymer form may be in itselastomeric state. If so, heat 56 is extracted to transition the polymerform from its elastomeric state to its glassy state prior to initiatingthe lay up of the composite materials.

The lay up of composite materials, which are themselves typicallypolymers, on a form is a well known manufacturing process. Fiberreinforcement materials could consist of carbon/graphite, aramid, orglass fibers, among others in common use today, which are readilyavailable in many different forms including yarns, rovings, choppedstrands, woven fabric, mats, etc. Filament winding could also be used.Matrix materials could include any of those commonly available today,including epoxies, polyurethanes, polyamides, BMIs (bismaleimides), etc.Common hand layup processes could also be used. The choice ofreinforcement type and resin will depend first on structural designrequirements, and second on convenience

In step 3, the composite material 54 is then cured, set, hardened orotherwise solidified (“solidified”) while on the form to create theone-piece composite wing 50. The process will depend on the requirementsof the resin that was chosen, and a variety of possibilities exist. Some(for example some epoxies) will solidify in air at room temperature,some resins will require oven baking, while others still will require anautoclave to provide both heat and pressure for the process. During theprocess, the form may be either above or below its Tg. It is onlynecessary that enough support be given the part that it does not warp orotherwise deform under gravitational loading before the composite matrixhas solidified.

In step 4, the polymer form 50 is drawn from inside the composite wingshell 50. Because die form is not “designed to draw” it must deformwithout damaging either the composite wing or itself. Accordingly, thepolymer form must be in its elastomeric state. If the polymer form isnot in its elastomeric state alter the solidification process, heat 58is applied to transition to its elastomeric state. The transition fromits glassy to its elastomeric state reduces the polymer form's Young'sModulus by at least 2-3 orders of magnitude making it quite pliable sothat the form can be draw from the wing shell. Note, producing the formwith a hollow core also makes it easier to drawn the form from the wingshell. The Tg of the polymer form will be chosen such that it is lowerthan the Tg of the composite matrix so as to avoid softening ordecomposing the finished composite part.

It is the elastomeric properties of the form that allow it to be removedfrom the finished composite part. The form will warp and stretch out ofits “original” shape while being removed from the composite wing shell.Once removed, the polymer form returns to its original shape and may bereused to form another one-piece composite wing shell 50 of the samesize and shape. After repeated use the form may lose its shape and bediscarded. Alternately, because the manufacturing processes that can beused to produce the form are so inexpensive the forms may be used onlyonce and discarded.

It is important to note that if a SMP is used for the form, its“memorization” properties are not used. The form has only one shape;that of the one-piece composite wing shell. The form will warp andstretch out of this shape when removed but will return to its originalshape naturally, without requiring or relying on the speciallyformulated properties of SMPs for removal. The SMP transitions from itsglassy state to its elastomeric state without relaxing to a differentmemorized shape. In effect, the original shape is the memorized shape.In this application, a SMP is used because it is designed to providegood mechanical and other properties in both its glassy and elastomericstates, rather than for its shape memory properties.

A process of manufacture of one-piece composite wing shells 100 havingtaper, twist and camber using a two-piece form including a shapedpolymer form 102 that does not draw and a rigid insert 104 designed todraw is illustrated in FIG. 4.

In step 1, a rigid insert 104 designed to draw from polymer form 102 isproduced. The insert may be machined from metal, engineered plastics ora ceramic. The insert may be an SLS ‘grown’ plastic part, or it may beproduced by any other common manufacturing process.

In step 2, the polymer form 102 is produced using the same processdescribed above except that insert 104 is used as a core when the formis made. In this manner, insert 104 is “inserted” in-situ during theproduction of the polymer form. Alternately, a standard tooling insertcould be used to produce the polymer form, removed and a differentinsert placed in the form. Polymer form 102 does not draw from thecomposite wing shell 100 but insert 104 is shaped so that it will drawout of the form, i.e. it is designed to draw. For example, the form mayhave a specified twist for the wing design but the insert does not havetwist. Alternately, the form may have both taper and camber for the wingdesign but the insert does not have at least one of taper or camber.

In step 3, composite materials 106 are laid up on polymer form 102.Depending upon the size and shape of the composite wing shell, the rigidinsert 104 may provide sufficient stiffness to lay up the compositematerials. In these cases, the polymer may remain in its elastomericstate. The insert has stiffness or Young's Modulus at least 10× that ofthe polymer in its elastomeric state and more typically greater than100× or 1,000×. This removes the requirement of having a polymer that isstable in both its elastomeric and glassy states and simplifies themanufacturing process by removing the transition back-and-forth, thepolymer remains in its elastomeric state throughout the process. Inother cases, it may be desired to use both the rigid insert and have thepolymer form in its glassy state to lay up the composite materials. Inthis situation, if after curing or drawing from a previouslymanufactured composite shell the polymer form is in its elastomericstate heat is extracted to transition the polymer form from itselastomeric state to its glassy state prior to initiating the lay up ofthe composite materials.

In step 4, the composite material 106 is solidified while on the form tocreate the one-piece composite wing 100 as described above.

In step 5, the insert 104 is drawn from polymer form 102. The form ispreferably in its elastomeric state to avoid damage. Although the insert104 is rigid and cannot warp or twist, because it is “design to draw” itcan be pulled directly out of form 102.

In step 6, the polymer form 102 is drawn from inside the composite wingshell 100. Because the form is not “designed to draw” it must deformwithout damaging either the composite wing shell or itself. Accordingly,the polymer form must be in its elastomeric state. If the polymer formis not in its elastomeric state after the cure process, heat is appliedto transition to the elastomeric state. The hollow core allows the formto deform more readily and thus simplifies the drawing process. Onceremoved, the polymer form returns to its original shape and may bereused to form another one-piece composite wing shell 100 of the samesize and shape. The insert 104 is inserted back into the polymer form102, preferably in its elastomeric state, and process repeats steps 3through 6. After repeated use the form may lose its shape and bediscarded. Alternately, because the manufacturing processes that can beused to produce the form are so inexpensive the forms may be used onlyonce and discarded.

The low-cost manufacture of one-piece composite wings 200 and 202 fromthe wing shells 204 of the type manufactured with either of thedescribed polymer form processes is shown in FIGS. 5 a and 5 b. In oneembodiment, one or more internal structural elements 206 such asrectangular metal or PMC (polymer matrix composite) tubes are placedinside the composite wing skin to provide additional structural support.In many cases, a single structural element running down the so-called“load line” of the wing if it is possible to fit it there should besufficient. The load line is where the center of lift occurs on thewing, and it is well known that the load line is at the quarter-chordlength from the leading edge of the wing. In both embodiments, theinside of the composite wing shell is filled with a polymeric foammaterial 208. The polymer foam may be an injected or cast open or closedcell foam, or it may be a cast syntactic foam. The choice is a matterfirst of structural needs, and second convenience. The foam serves toprovide buckling reinforcement for the composite wing shell, and alsoglues the structural element 206 in place if one is required. The foamsolidifies to form a solid wing.

A process of manufacture of a one-piece composite valve 300, similar tothat depicted in FIG. 1, using a two-piece form including a shapedpolymer form 302 that does not draw and a rigid insert 304 designed todraw is illustrated in FIG. 6. The process is the same as we describedfor the manufacture of the composite wing shells. In step 1, rigidinsert 304 is produced using a standard machining or casting process. Asshown the insert is suitably provided with a slight taper to make iteasier to draw from the polymer form. In step 2, the polymer form 302 isproduced using the insert 304 as a core. In step 3, composite materials306 are laid up on the assembled form with the polymer in either itselastomeric or glassy state depending on the requirements of aparticular application. In step 4, the composite materials 306 aresolidified to create composite valve 300. In step 5, the insert 304 isdrawn from polymer form 302. The form is preferably in its elastomericstate to avoid damage. Although the insert 304 is rigid and cannot warpor twist because it is “design to draw” it can be pulled directly out ofform 302 from the larger end. In step 6, the polymer form 302 is drawnin its elastomeric state from composite valve 300 causes the polymer towarp and twist as it is removed. Once removed the polymer returns to itsoriginal shape. The insert can be placed back into the form and the formreused to form multiple composite valves 300 of the same size and shape.Alternately, the form and possibly the insert can be discarded.

While several illustrative embodiments of the invention have been shownand described, numerous variations and alternate embodiments will occurto those skilled in the art. Such variations and alternate embodimentsare contemplated, and can be made without departing from the spirit andscope of the invention as defined in the appended claims.

1. A process of manufacturing a one-piece composite part, comprising thesteps of: (a) fabricating a shape memory polymer (SMP) into the shape ofa form for a one-piece composite part and then solidifying the polymerform into its glassy state, said form having a shape that does not drawfrom the composite part; (b) with the SMP form in its glassy state,laying up a composite material on the form; (c) solidifying thecomposite material to create a one-piece composite part; (d) heating theSMP form to transition from its glassy state to its elastomeric statewithout changing shape; and (e) drawing the form in its elastomericstate from the one-piece composite part thereby deforming the form as itis removed, said form returning to its original shape for the one-piececomposite part upon removal.
 2. The process of manufacture of claim 1,wherein the step of forming the SMP into a form comprises a compressionmolding or injection molding.
 3. The process of manufacture of claim 1,wherein the process uses a SMP without using its shape-memoryproperties.
 4. The process of manufacture of claim 1, furthercomprising: (f) cooling the form to transition from its elastomericstate to its glassy state; and (g) repeating steps (b) through (f) withthe same form to produce a plurality of the same composite parts.
 5. Aprocess of manufacturing a one-piece composite wing shell, comprisingthe steps of: (a) forming a shape memory polymer (SMP) into the shape ofa form for a one-piece composite wing shell and solidifying the polymerform into its glassy state, said form having a twist or taper and camberthat does not draw from the composite wing shell; (b) with the SMP formin its glassy state, laying up a composite material on the form; (c)solidifying the composite material to form a one-piece composite wingshell; (d) heating the form to transition from its glassy state to itselastomeric state without changing shape; and (e) drawing the form inits elastomeric state from the one-piece composite wing shell therebydeforming the form as it is removed, said form returning to its originalshape upon removal.
 6. The process of manufacture of claim 5, whereinsaid composite wing shell has a specified twist, taper and camber. 7.The process of manufacture of claim 5, further comprising: (f) coolingthe form to transition from its elastomeric state to its glassy state;and (g) repeating steps (b) through (f) with the same form to produce aplurality of the same composite wing shells.
 8. The process ofmanufacture of claim 7, further comprising for each said composite wingshell, (h) injecting polymer foam inside the composite wing shell toform a one-piece composite wing with the specified twist or taper andcamber.
 9. The process of manufacture of claim 8, further comprising foreach said composite wing shell inserting a wing box into the compositeshell prior to injecting the foam.
 10. The process of manufacture ofclaim 5, further comprising for each said composite wing shell, (f)injecting foam inside the composite wing shell to form a one-piececomposite wing with the specified twist or taper and camber.
 11. Theprocess of manufacture of claim 10, wherein the foam comprises open orclosed cell foam or syntactic foam.